Fibrous reinforcement of concrete through the addition of fibers to an admixture of concrete and/or other concrete-like materials has long been used in the construction industry to improve plastic shrinkage crack resistance and post-peak flexural strength. For example, Goldfein U.S. Pat. No. 3,645,961 discloses an impact resistant concrete product comprising an admixture of inorganic hydraulic cement and selected aggregate, together with a plurality of selected fibers substantially uniformly distributed throughout the admixture. Similarly, Zonsveld et al. U.S. Pat. No. 3,591,395 is directed toward products with improved bending strength made from concrete, mortar, cement or plaster of Paris and up to 2% by weight of fibrillated polypropylene film. However, few of these fibers, most of which are polymeric, steel and/or fiberglass, have included additives to further enhance performance of the fibers in the concrete. That is, most of the fibers employed are strictly used for concrete reinforcement.
There are, however, at least a few products and patents which do incorporate various additives into fibers which are then admixed with concrete or some other concrete-like material. For example, at least one product, available from Esbjerg Tovvaerksfabrik A/S of Esbjerg, Denmark under the tradename Polycrete, at least partially encapsulates calcium carbonate in polypropylene fibers which are then used for reinforcement of Portland Cement concrete. The calcium carbonate provides a chemical linkage between the fibers and the concrete matrix.
The patent literature also discloses the use of various additives in fibers for the reinforcement of concrete. This list of patents includes Valle European Patent Publication No. 0,470,829 A1, Pairaudeau et al. U.S. Pat. No. 4,111,710, Camprincoli et al. U.S Pat. No. 4,132,556, Burgress et al. U.S. Pat. No. 4,263,365, Normura et al. U.S. Pat. No. 4,407,986, Kobayashi et al. U.S. Pat. No. 4,565,840, Hefner, Jr. et al. U.S. Pat. No. 4,611,015, Soroushian et al. U.S. Pat. No. 4,902,347, Sawanobori et al. U.S. Pat. No. 4,916,012, Magnani U.S. Pat. No. 4,960,616, Smith et al. U.S. Pat. No. 4,961,790, and Mizobe et al. U.S. Pat. No. 4,968,561. However, none of these patents or publications teach or even suggest the use of an antimicrobial agent as the additive to be incorporated into the fibers.
Notably, this is the case even though antimicrobial agents have been used directly in concrete for some time to provide a more durable concrete having an increased resistance to biological attack from fungi, bacteria, mold, mildew, etc. Antimicrobial agents are also known to reduce odors and provide more hygenic environments where they are utilized. Presently, as noted in Valle U.S. Pat. No. 5,203,629, antimicrobial activity in concrete has been at least partially controlled through the use of fungicidal, germicidal and insecticidal admixtures. However, no antimicrobial agents have ever been implanted into or coated onto fibers which were then admixed in concrete. That is, none of these patents or publications suggest or make any effort whatsoever to combine (1) the implantation of at least one antimicrobial chemical agent into fibers with (2) the blending of the resultant composite fiber in an isotropic, three-dimensional manner into concrete or like materials to simultaneously effect (a) antimicrobial activity and (b) reinforcement of the concrete.
Such fiber-reinforced concrete having antimicrobial agents incorporated into the fibers themselves may serve several useful purposes. For instance, the antimicrobial agents could effectively reduce bacteria in food processing plants, hospitals, institutional kitchens, athletic locker rooms and other areas susceptible to biological attack, but where extraordinary cleanliness is required. These agents could also reduce mold and mildew which may cause discoloration and odor in slabs on grade, stucco and roofing materials in damp or wet climates. Still further, such antimicrobial agents in the fibers themselves could prevent bacteria in concrete from digesting liquid or gaseous effluent and then secreting toxic materials which attack the concrete such as, for example, sulfuric acid which has been known to attack concrete or stucco.
Thus, the need exists for a fiber-reinforced concrete having at least one antimicrobial agent incorporated in the fibers which are dispersed therein.